Dry chemistry cascade immunoassay and affinity assay

Abstract

A method is described for performing an affinity assay comprising contacting a sample to be assayed for the presence of an analyte with a dry reagent containing the analyte (hapten, antigen, antibody, receptor, or complementary polynucleotide) bound to a reaction cascade initiator, an antibody or other binding pair partner reactive with said analyte, and magnetic particles, to form an assay mixture in a reaction chamber, incubating the assay mixture, applying an oscillating or moving static magnetic field to the assay mixture, activating the reaction cascade initiator to initiate a reaction cascade, monitoring the response of the magnetic particles to the oscillating or moving static magnetic field to provide a time varying signal, and determining the analyte concentration of the sample by analysis of the time varying signal, as well as a kit for performing the assay and a diagnostic system for performing the assay.

What is claimed as new and desired to be secured by Letters patent of the United States is: 
     
       1. A method for performing an affinity assay comprising: a) contacting a sample to be assayed for the presence of an analyte with a dry reagent comprising: 1) an analyte-conjugated initiator comprising said analyte conjugated to a reaction cascade initiator, wherein said reaction cascade initiator is an initiator for a reaction cascade selected from the group consisting of a lytic cascade and a coagulation cascade;   2) a binding pair partner which specifically binds to said analyte; and   3) magnetic particles, to form an assay mixture comprising (i) said binding pair partner bound to said analyte, (ii) said binding pair partner bound to said analyte-conjugated initiator, and (iii) unbound analyte-conjugated initiator, wherein either a steric or exclusion mechanism is selected to couple a binding pair interaction in said assay mixture with said reaction cascade, wherein:       in said steric mechanism, when the binding pair partner binds with the analyte-conjugated initiator, the reaction cascade initiator is sterically blocked from initiating the reaction cascade, providing a rate for the reaction cascade which is directly proportional to the amount of unbound analyte-conjugated initiator, and thus directly proportional to amount of said analyte in the sample, and   in said exclusion mechanism, the binding pair partner that specifically binds with said analyte is bound to a solid support and any analyte present in said sample will compete with analyte-conjugated initiator for reaction with said binding pair partner, wherein initiation of the reaction cascade by said unbound analyte-conjugated initiator provides a rate of the reaction cascade which is directly proportional to the amount of said analyte in the sample;   b) separating the solid support including (i) said binding pair partner bound to said analyte and (ii) said binding pair partner bound to said analyte-conjugated initiator from (iii) said unbound analyte-conjugated initiator, when said exclusion mechanism is employed;   c) incubating either (i) said assay mixture when said steric mechanism is employed or (ii) said unbound analyte-conjugated initiator when said exclusion mechanism is employed, with one or more cascade components, to form an incubation mixture, wherein said one or more cascade components is present in an amount sufficient to make initial reaction of said initiator a rate-limiting step in said reaction cascade, wherein said one or more cascade components are sufficient to complete said reaction cascade upon initiation by said initiator, and wherein when said exclusion mechanism is employed, said one or more cascade components are added to said assay mixture after said contacting step, or when said steric mechanism is employed, said one or more cascade components are either present in said dry reagent prior to said contacting step or added to said assay mixture after said contacting step;   d) applying a magnetic field to said assay mixture, wherein said magnetic field is an alternating magnetic field selected from the group consisting of an oscillating magnetic field, a rotating magnetic field and a moving static magnetic field;   e) activating said reaction cascade initiator to initiate said reaction cascade, wherein when said reaction cascade is a coagulation cascade, the coagulation cascade proceeds to formation of a fibrin clot and wherein when said reaction cascade is a lytic cascade, the lytic cascade proceeds by lysis of a fibrin clot;   f) monitoring a response of said magnetic particles to the magnetic field by an optical means to provide a time varying optical signal; and   g) determining a concentration of said analyte in said sample by analysis of said time varying optical signal.   
     
     
       2. The method of claim 1, wherein said reaction cascade initiator is activated by exposure to light or heat. 
     
     
       3. The method of claim 1, wherein said reaction cascade initiator is activated by transferring said assay mixture, when said steric mechanism is employed, or said unbound analyte conjugated initiator, when said exclusion mechanism is employed, from a first portion of said reaction chamber to a second portion of said reaction chamber, wherein one or more inhibitors are present in said first portion to prevent said initiator from being activated, and wherein one or more neutralizers are present in said second portion to neutralize said one or more inhibitors and activate said initiator. 
     
     
       4. The method of claim 1, wherein said binding pair partner is an antibody. 
     
     
       5. The method of claim 1, wherein said solid support is a surface of a reaction slide in which the assay is performed. 
     
     
       6. The method of claim 1, wherein said solid support is said magnetic particles. 
     
     
       7. The method of claim 1, wherein said solid support is non-magnetic particles. 
     
     
       8. The method of claim 2, wherein said reaction cascade initiator is an enzyme in said reaction cascade. 
     
     
       9. The method of claim 1, wherein said optical means comprises a photodetector and a light-emitting source. 
     
     
       10. The method of claim 9, wherein said light-emitting source is a 900 nanometer light-emitting diode. 
     
     
       11. The method of claim 1, wherein said magnetic field is a rotating magnetic field. 
     
     
       12. The method of claim 1, wherein said magnetic field is an oscillating magnetic field. 
     
     
       13. The method of claim 1, wherein said magnetic field is a moving static magnetic field. 
     
     
       14. The method of claim 1, wherein said coagulation cascade is selected from the group consisting of human blood coagulation cascade, bovine blood coagulation cascade, porcine blood coagulation cascade, bovine milk coagulation cascade, horseshoe crab hemolymph cascade, and insect blood coagulation cascade. 
     
     
       15. The method of claim 1, wherein said one or more cascade components are provided as a pooled plasma sample. 
     
     
       16. The method of claim 1, wherein said reaction cascade is a mammalian blood coagulation cascade. 
     
     
       17. The method of claim 1, wherein said binding pair partner is a receptor molecule. 
     
     
       18. The method of claim 17, wherein said steric mechanism is employed. 
     
     
       19. The method of claim 17, wherein said exclusion mechanism is employed. 
     
     
       20. The method of claim 1, wherein said binding pair partner is a ligand. 
     
     
       21. The method of claim 1, wherein said dry reagent contains a Factor IXa conjugate. 
     
     
       22. The method of claim 1, wherein the analyte is a low molecular weight molecule of <2000 Daltons. 
     
     
       23. The method of claim 1, wherein the analyte is an antiarrhythmic drug. 
     
     
       24. The method of claim 1, wherein the analyte is a hapten. 
     
     
       25. The method of claim 1, wherein the analyte is a peptide. 
     
     
       26. The method of claim 1, wherein the binding pair partner is an antibody and the analyte is a cell surface antigen. 
     
     
       27. The method of claim 1, wherein the binding pair partner is an antibody or antigen and the analyte is an antigen or antibody, respectively. 
     
     
       28. The method of claim 1, wherein said dry reagent contains a thrombin conjugate. 
     
     
       29. The method of claim 1, wherein said dry reagent contains a Factor Xa conjugate. 
     
     
       30. The method of claim 1, wherein said dry reagent contains a Factor IXa conjugate. 
     
     
       31. The method of claim 1, wherein said dry reagent contains a Russell's viper venom conjugate. 
     
     
       32. The method of claim 1, further comprising diluting said sample prior to said step of contacting the sample with the dry reagent. 
     
     
       33. A method for performing an affinity assay comprising: a) contacting a sample to be assayed for the presence of an analyte with a dry reagent comprising: 1) a partner-conjugated initiator comprising a binding pair partner, which specifically binds with said analyte, conjugated to a reaction cascade initiator, wherein said reaction cascade initiator is an initiator for a reaction cascade selected from the group consisting of a lytic cascade and a coagulation cascade; and   2) magnetic particles, to form an assay mixture comprising (i) said partner-conjugated initiator bound to said analyte, and (ii) unbound partner-conjugated initiator, wherein a steric mechanism is selected to couple a binding pair interaction in said assay mixture with said reaction cascade, wherein:       in said steric mechanism, when said partner-conjugated initiator binds with said analyte, the reaction cascade initiator is sterically blocked from initiating the reaction cascade, providing a rate for the reaction cascade which is directly proportional to the amount of unbound partner-conjugated initiator, and thus inversely proportional to amount of said analyte in the sample;   b) incubating said assay mixture with one or more cascade components, to form an incubation mixture, wherein said one or more cascade components is present in an amount sufficient to make initial reaction of said initiator a rate-limiting step in said reaction cascade, wherein said one or more cascade components are sufficient to complete said reaction cascade upon initiation by said initiator, and wherein said one or more cascade components are either present in said dry reagent prior to said contacting step or added to said assay mixture after said contacting step;   c) applying a magnetic field to said assay mixture, wherein said magnetic field is an alternating magnetic field selected from the group consisting of an oscillating magnetic field, a rotating magnetic field and a moving static magnetic field;   d) activating said reaction cascade initiator to initiate said reaction cascade, wherein when said reaction cascade is a coagulation cascade, the coagulation cascade proceeds to formation of a fibrin clot and wherein when said reaction cascade is a lytic cascade, the lytic cascade proceeds by lysis of a fibrin clot;   e) monitoring a response of said magnetic particles to the magnetic field by an optical means to provide a time varying optical signal; and   f) determining a concentration of said analyte in said sample by analysis of said time varying optical signal.   
     
     
       34. A kit, for performing an affinity assay, comprising: a reaction slide having a reaction chamber;   a dry reagent contained in said reaction chamber, comprising an analyte to be assayed conjugated to a reaction cascade initiator, a binding pair partner that specifically binds with said analyte, and magnetic particles; wherein said reaction cascade initiator is an initiator for a reaction cascade selected from the group consisting of a lytic cascade and a coagulation cascade;   an amount of one or more additional cascade components effective to complete said reaction cascade upon initiation;   magnetic field generating means and optical means; and   means for amplifying and processing of a signal from said optical means to determine concentration of an analyte in a sample, wherein said signal represents a response of magnetic particles in a magnetic field generated by said magnetic field generating means.   
     
     
       35. The kit of claim 34, where said binding pair partner is an antibody or antigen. 
     
     
       36. The kit of claim 34, where said binding pair partner is a receptor or ligand. 
     
     
       37. The kit of claim 34, wherein said optical means comprises an illuminating source in the near infrared and a detection means. 
     
     
       38. The kit of claim 37, wherein said initiator is a light activated initiator and wherein said optical means further comprises an ultraviolet light source for activation of the initiator. 
     
     
       39. A method for performing an affinity assay comprising: a) contacting a sample to be assayed for the presence of an analyte having more than 1 binding region with a first dry reagent to form an assay mixture in a first reaction chamber, said first dry reagent comprising:   1) a first binding pair partner immobilized on a solid support, wherein said first binding pair partner specifically binds with a first binding region of said analyte, and   2) a second binding pair partner that specifically binds with a second binding region of said analyte, wherein said second binding pair partner is conjugated to a reaction cascade initiator, wherein said reaction cascade initiator is an initiator for a reaction cascade selected from the group consisting of a lytic cascade and a coagulation cascade;   b) incubating said assay mixture to form (a) immobilized complexes of first binding pair partner/analyte/conjugated second binding pair partner and (b) free conjugated second binding pair partner;   c) transferring said free conjugated second binding pair partner to a second reaction chamber that contains a second dry reagent comprising magnetic particles and an effective amount of one or more additional cascade components to complete said reaction cascade upon initiation;   d) activating said reaction cascade initiator to initiate said reaction cascade, wherein when said reaction cascade is a coagulation cascade, the coagulation cascade proceeds to formation of a fibrin clot and wherein when said reaction cascade is a lytic cascade, the lytic cascade proceeds by lysis of a fibrin clot;   e) monitoring a response of said magnetic particles to an applied alternating magnetic field selected from the group consisting of an oscillating magnetic field, a rotating magnetic field and a moving static magnetic field by optical means to provide a time varying optical signal; and   f) determining a concentration of said analyte in said sample by analysis of said time varying optical signal.   
     
     
       40. The method of claim 39, wherein said analyte is Apolipoprotein B, said first binding pair partner is a polyclonal antibody specific for a first epitope of Apolipoprotein B, said initiator is thrombin, said second antibody bound to said initiator is a monoclonal antibody having specificity for a second epitope of Apolipoprotein B, said solid support is magnetic particles, and said additional cascade component is fibrinogen, wherein: said second dry reagent further comprises a buffer and wherein said solid support of said first dry reagent is retained in said first reaction chamber by application of a magnetic field just prior to transfer of said free conjugated second binding pair partner to said second reaction chamber.   
     
     
       41. The method of claim 39, wherein said analyte is CKMB, said first binding pair partner is an antibody specific for a "B" region epitope of CKMB, said solid support is magnetic particles, said initiator is Russell's viper venom, and said second binding pair partner is an antibody specific for a "M" region epitope of CKMB, wherein; said one or more additional cascade components of said second dry reagent are Clotting Factor X, Factor V, phospholipid, prothrombin, calcium and fibrinogen, and wherein said second dry reagent further comprises a buffer; wherein said solid support of said first dry reagent is retained in said first reaction chamber by application of a magnetic field just prior to transfer of said free conjugated second binding pair partner to said second reaction chamber.   
     
     
       42. The method of claim 39, wherein said initiator activation step comprises illuminating said reaction cascade initiator with ultraviolet light. 
     
     
       43. The method of claim 39, wherein said one or more additional cascade components are provided as a pooled plasma sample. 
     
     
       44. The method of claim 39, wherein said analyte is an antigen, said first binding pair partner is a polyclonal antibody and said second pair partner is a monoclonal antibody. 
     
     
       45. The method of claim 39, wherein said dry reagent contains a Factor IXa conjugate. 
     
     
       46. The method of claim 39, wherein the analyte is selected from the group consisting of high molecular weight molecules of >2000 Daltons, cells, cell fragments and viruses. 
     
     
       47. The method of claim 39, wherein the analyte is an apolipoprotein. 
     
     
       48. The method of claim 39, wherein the analyte is a protein. 
     
     
       49. The method of claim 39, wherein the analyte is selected from the group consisting of lipoproteins, apolipoproteins, hormones, enzymes, external cell signal and structural elements, internal cell signal and structural elements and polynucleotides. 
     
     
       50. The method of claim 39, wherein said dry reagent contains a thrombin conjugate. 
     
     
       51. The method of claim 39, wherein said dry reagent contains a Russell's viper venom conjugate or a Factor IXa conjugate. 
     
     
       52. The method of claim 39, wherein said dry reagent contains a Factor Xa conjugate. 
     
     
       53. The method of claim 39, further comprising diluting the sample prior to said step of contacting the sample with the dry reagent. 
     
     
       54. A method for performing an affinity assay comprising: a) contacting a sample to be assayed for the presence of an analyte having more than 1 binding region with a dry reagent to form an assay mixture in a reaction chamber, said dry reagent comprising: 1) a first binding pair partner immobilized on a solid support, wherein said first binding pair partner specifically binds with a first binding region of said analyte, and   2) a second binding pair partner that specifically binds with a second binding region of said analyte, wherein said second binding pair partner is conjugated to a reaction cascade initiator, wherein said reaction cascade initiator is an initiator for a reaction cascade selected from the group consisting of a lytic cascade and a coagulation cascade and wherein said reaction cascade initiator is a triggerable initiator;     b) incubating said assay mixture to form (a) immobilized complexes of first binding pair partner/analyte/conjugated second binding pair partner and (b) free conjugated second binding pair partner;   c) washing said free conjugated second binding pair partner out of said reaction chamber with a wash solution to provide said immobilized complexes of first binding pair partner/analyte/conjugated binding pair partner, magnetic particles and said wash solution remaining in said reaction chamber;   d) providing to said reaction chamber an effective amount of one or more cascade components to complete said reaction cascade upon initiation;   e) triggering said reaction cascade initiator to initiate said reaction cascade, wherein when said reaction cascade is a coagulation cascade, the coagulation cascade proceeds to formation of a fibrin clot and wherein when said reaction cascade is a lytic cascade, the lytic cascade proceeds by lysis of a fibrin clot;   f) monitoring a response of said magnetic particles to an applied alternating magnetic field selected from the group consisting of an oscillating magnetic field, a rotating magnetic field and a moving static magnetic field by optical means to provide a time varying optical signal; and   g) determining a concentration of said analyte in said sample by analysis of said time varying optical signal.   
     
     
       55. The method of claim 54, wherein said triggering step comprises illuminating said reaction cascade initiator with ultraviolet light. 
     
     
       56. The method of claim 54, wherein said analyte is an antigen, said first binding pair partner is a polyclonal antibody and said second pair partner is a monoclonal antibody. 
     
     
       57. A kit, for performing an affinity assay, comprising: a reaction slide having two reaction chambers;   a dry reagent contained in each of said reaction chambers, comprising a first dry reagent in a first reaction chamber, comprising a first binding pair partner immobilized on a solid support, wherein said first binding pair partner specifically binds with a first binding region of an analyte, and a second binding pair partner that specifically binds with a second binding region of said analyte, wherein said second binding pair partner is conjugated to a reaction cascade initiator, wherein said reaction cascade initiator is an initiator for a reaction cascade selected from the group consisting of a lytic cascade and a coagulation cascade,   and a second dry reagent in a second reaction chamber comprising magnetic particles and an effective amount of one or more additional cascade components to complete a cascade reaction upon initiation; and   magnetic field generating means and optical means.   
     
     
       58. The kit of claim 57, wherein said optical means comprises an illuminating source in the near infrared and a detection means. 
     
     
       59. The kit of claim 57, wherein said initiator is a light activated initiator and wherein said optical means further comprises an ultraviolet light source for activation of the initiator. 
     
     
       60. A diagnostic system for performing affinity assays comprising: a) a reaction slide comprising: 1) a sample well for application of a sample to be analyzed;   2) one or more reaction chambers connected to and in fluid communication with the sample well; and   3) dry chemistry reagents and magnetic particles in each of the one or more reaction chambers, wherein the dry chemistry reagents comprise an analyte conjugated to a reaction cascade initiator, a binding pair partner which specifically binds to said analyte, and one or more coagulation cascade reagents;     b) one or more means of generating a rotating magnetic field;   c) one or more optical detection systems comprising illumination means and detection means; and   d) one or more means for amplifying and processing of a signal from each of said optical detection systems to determine the concentration of one or more analytes in a sample, wherein said signal represents a response of magnetic particles in said rotating magnetic field.   
     
     
       61. The diagnostic system of claim 60, wherein said sample well of said reaction slide is in fluid communication with a parallel array of reaction chambers, each containing a different dry chemistry formulation; a plurality of said means for generation of rotating magnetic fields, with one for each separate reaction chamber; a plurality of optical detection systems, with one for each separate reaction chamber; and amplification and signal processing means for analysis of multiple analytes in the sample. 
     
     
       62. The diagnostic system of claim 60, also comprising means for delivery of ultraviolet light to said reaction chamber. 
     
     
       63. The diagnostic system of claim 60, wherein each of said one or more reaction chambers comprises: a first chamber for performing an affinity reaction, a second chamber adjacent to and in fluid communication with said first chamber for performing a coagulation cascade reaction, means for transferring liquid from said first chamber to said adjacent second chamber, and a rotating magnetic field for each chamber. 
     
     
       64. The diagnostic system of claim 61, comprising a parallel array of first chambers for performing affinity reactions, means for transferring liquid from each of the first chambers to a second chamber adjacent to each of said first chambers and in fluid communication therewith for performing a coagulation cascade reaction, magnetic particles in each chamber, and a rotating magnetic field for each chamber, allowing for analysis of multiple analytes in the sample. 
     
     
       65. The diagnostic system of claim 64, wherein said parallel array of reaction chambers contain, individually, a dry reagent formulation for analysis of Apo B-100, Apo A-1 and Apo(a), respectively, for assessment of atherosclerosis risk. 
     
     
       66. The diagnostic system of claim 64, wherein said parallel array of reaction chambers contain, individually, a dry reagent formulation for analysis of CKMB, troponin T, myoglobin, fibrinopeptide A, and fibrinogen, respectively for confirmation of acute myocardial infarction. 
     
     
       67. The diagnostic system of claim 60, further comprising a heating means for temperature control and a means for identification of reaction slide and sample. 
     
     
       68. The diagnostic system of claim 60, further comprising a vent in said reaction chamber, wherein said vent is covered by a hydrophobic membrane, and a means for applying a vacuum to said vent to provide a motive force for moving the sample from said sample well to said reaction chamber. 
     
     
       69. The diagnostic system of claim 60, further comprising an inlet in said sample well, a vent in said reaction chamber, wherein said vent is covered by a hydrophobic membrane, and a means for applying pressure to said inlet to provide a motive force for moving the sample from said sample well to said reaction chamber. 
     
     
       70. The diagnostic system of claim 60, further comprising an inlet in said sample well with a luer adapter affixed thereto, a vent in said reaction chamber, wherein said vent is covered by a hydrophobic membrane, and a syringe means docked to said luer adapter for applying pressure to a liquid sample to provide motive force for moving the sample into said sample well and into said reaction chamber. 
     
     
       71. A diagnostic system for performing affinity assays comprising: a) a reaction panel test card comprising: 1) a sample well for application of a sample to be analyzed;   2) a plurality of reaction chambers connected to and in fluid communication with the sample well; and   3) one or more dry chemistry reagent mixtures and magnetic particles, in each of the reaction chambers, wherein at least one of said one or more dry chemistry reagent mixtures must comprise either (i) an analyte conjugated to a reaction cascade initiator, a binding pair partner which specifically binds to said analyte, and magnetic particles, or (ii) a binding pair partner which specifically binds with said analyte and is conjugated to a reaction cascade initiator, such that binding of said analyte to said binding pair partner sterically interferes with initiator molecule function, and magnetic particles; and wherein at least one of said one or more dry chemistry reagent mixtures must comprise a coagulation cascade reagent;       b) one or more means of generating a rotating magnetic field;   c) one or more optical detection systems comprising illumination means and detection means; and   d) means for amplifying and processing of signals from said optical detection systems to determine the concentrations of analytes in a sample, wherein said signals represent responses of magnetic particles in said one or more rotating magnetic fields.   
     
     
       72. The system of claim 71, wherein each dry chemistry reagent contained in each of said plurality of reaction chambers has been subjected to preparation conditions which differ from the preparation conditions of the other dry chemistry reagents contained in the rest of said plurality of reaction chambers prior to placement on the panel test card and connection to said sample well. 
     
     
       73. A method for performing an affinity assay comprising: a) contacting a sample to be assayed for the presence of an analyte with a dry reagent comprising: 1) an analyte-conjugated zymogen comprising said analyte conjugated to a zymogen of a reaction cascade, wherein said reaction cascade is selected from the group consisting of a lytic cascade and a coagulation cascade;   2) a binding pair partner which specifically binds to said analyte;   3) a reaction cascade initiator, wherein said reaction cascade initiator is an initiator for said reaction cascade and is any enzyme from said reaction cascade that is higher in said reaction cascade than said zymogen; and   4) magnetic particles, to form an assay mixture in a reaction chamber comprising (i) said binding pair partner bound to said analyte, (ii) said binding pair partner bound to said analyte-conjugated zymogen, (iii) unbound analyte-conjugated zymogen and (iv) said reaction cascade initiator, wherein either a steric or exclusion mechanism is selected to couple a binding pair interaction in said assay mixture with said reaction cascade, wherein:       in said steric mechanism, when the binding pair partner binds with the analyte-conjugated zymogen, the zymogen is sterically blocked from participating in the reaction cascade, such that upon activation of said reaction cascade initiator, the reaction cascade proceeds at a rate which is directly proportional to the amount of said unbound analyte-conjugated zymogen, and thus directly proportional to amount of said analyte in the sample, and   in said exclusion mechanism, the binding pair partner that specifically binds with said analyte is bound to a solid support and any analyte present in said sample will compete with said analyte-conjugated zymogen for reaction with said binding pair partner, wherein initiation of the reaction cascade by activation of said reaction cascade initiator provides a rate of the reaction cascade which is directly proportional to the amount of said unbound analyte-conjugated zymogen and thus directly proportional to the amount of said analyte in the sample;   b) separating the solid support including (i) said binding pair partner bound to said analyte and (ii) said binding pair partner bound to said analyte-conjugated zymogen from (iii) said unbound analyte-conjugated zymogen and said reaction cascade initiator, when said exclusion mechanism is employed;   c) incubating either (i) said assay mixture when said steric mechanism is employed or (ii) said unbound analyte-conjugated zymogen and reaction cascade initiator when said exclusion mechanism is employed, with one or more cascade components to form an incubation mixture,   wherein said one or more cascade components is present in an amount sufficient to make initial reaction of said zymogen activated by said reaction cascade initiator a rate limiting step in said reaction cascade and wherein said one or more cascade components are sufficient to complete said reaction cascade upon initiation, and   wherein when said exclusion mechanism is employed, said one or more cascade components are added to said assay mixture after said contacting step, or when said steric mechanism is employed, said one or more cascade components are either present in said dry reagent prior to said contacting step or added to said assay mixture after said contacting step;   d) applying a magnetic field to said assay mixture, wherein said magnetic field is an alternating magnetic field selected from the group consisting of an oscillating magnetic field, a rotating magnetic field and a moving static magnetic field;   e) activating said reaction cascade initiator to initiate said reaction cascade, wherein when said reaction cascade is a coagulation cascade, the coagulation cascade proceeds to formation of a fibrin clot, and wherein when said reaction cascade is a lytic cascade, the lytic cascade proceeds by lysis of a fibrin clot;   f) monitoring a response of said magnetic particles to the magnetic field by an optical means to provide a time varying optical signal; and   g) determining a concentration of said analyte in said sample by analysis of said time varying optical signal.   
     
     
       74. The method of claim 73 wherein said reaction cascade initiator is a triggerable enzyme that is higher in the reaction cascade than said zymogen bound to said analyte. 
     
     
       75. The method of claim 73, wherein said reaction cascade initiator is activated by exposure to light or heat. 
     
     
       76. The method of claim 73, wherein said binding pair partner is an antibody. 
     
     
       77. The method of claim 76, wherein said steric mechanism is employed. 
     
     
       78. The method of claim 76, wherein said exclusion mechanism is employed. 
     
     
       79. The method of claim 73, wherein said optical means comprises a photodetector and a light-emitting source. 
     
     
       80. The method of claim 79, wherein said light-emitting source is a 900 nanometer light-emitting diode. 
     
     
       81. The method of claim 73, wherein said magnetic field is a rotating magnetic field. 
     
     
       82. The method of claim 73, wherein said magnetic field is an oscillating magnetic field. 
     
     
       83. The method of claim 73, wherein said magnetic field is a moving static magnetic field. 
     
     
       84. The method of claim 73, wherein said coagulation cascade is selected from the group consisting of human blood coagulation cascade, bovine blood coagulation cascade, porcine blood coagulation cascade, bovine milk coagulation cascade, horseshoe crab hemolymph cascade, and insect blood coagulation cascade. 
     
     
       85. The method of claim 73, further comprising diluting the sample prior to said step of contacting the sample with the dry reagent. 
     
     
       86. A method for performing an affinity assay comprising: a) contacting a sample to be assayed for the presence of an analyte with a dry reagent comprising: 1) a partner-conjugated initiator comprising a binding pair partner that specifically binds with said analyte and is conjugated to a reaction cascade initiator, wherein said reaction cascade initiator is an initiator for a reaction cascade selected from the group consisting of a lytic cascade and a coagulation cascade; and   2) magnetic particles; to form an assay mixture in a reaction chamber, comprising (i) unbound partner-conjugated initiator, and (ii) said partner-conjugated initiator bound to said analyte,       wherein a steric mechanism is selected to couple a binding pair interaction in said assay mixture with said reaction cascade, such that when the partner-conjugated initiator binds to said analyte, the reaction cascade initiator is sterically blocked from initiating the reaction cascade, providing a rate for the reaction cascade which is directly proportional to the amount of said unbound partner-conjugated initiator and thus inversely proportional to amount of said analyte in the sample;   b) incubating said assay mixture with one or more cascade components to form an incubation mixture, wherein said one or more cascade components is present in an amount sufficient to make initial reaction of said initiator a rate-limiting step in said reaction cascade, wherein said one or more cascade components are sufficient to complete said reaction cascade upon initiation by said initiator, and wherein said one or more cascade components are either present in said dry reagent prior to said contacting step or added to said assay mixture after said contacting step;   c) applying a magnetic field to said assay mixture, wherein said magnetic field is an alternating magnetic field selected from the group consisting of an oscillating magnetic field, a rotating magnetic field and a moving static magnetic field;   d) activating said reaction cascade initiator to initiate said reaction cascade, wherein when said reaction cascade is a coagulation cascade, the coagulation cascade proceeds to formation of a fibrin clot and wherein when said reaction cascade is a lytic cascade, the lytic cascade proceeds by lysis of a fibrin clot;   e) monitoring a response of said magnetic particles to the magnetic field by an optical means to provide a time varying optical signal; and   f) determining a concentration of said analyte in said sample by analysis of said time varying optical signal.